From 3836c13d7a2f52dc703ab2cd06b8c867f071979f Mon Sep 17 00:00:00 2001
From: Nikita Kazmin <vonzshik@gmail.com>
Date: Thu, 29 Jan 2026 18:20:38 +0300
Subject: [PATCH] Fix reusing NpgsqlBatch with auto prepare

---
 src/Npgsql/NpgsqlBatchCommand.cs      |  8 ++++++--
 src/Npgsql/NpgsqlCommand.cs           | 13 +++++++------
 src/Npgsql/NpgsqlDataReader.cs        |  2 --
 test/Npgsql.Tests/AutoPrepareTests.cs | 27 +++++++++++++++++++++++++++
 4 files changed, 40 insertions(+), 10 deletions(-)

diff --git a/src/Npgsql/NpgsqlBatchCommand.cs b/src/Npgsql/NpgsqlBatchCommand.cs
index 17cec381b2..2812fdbead 100644
--- a/src/Npgsql/NpgsqlBatchCommand.cs
+++ b/src/Npgsql/NpgsqlBatchCommand.cs
@@ -172,7 +172,7 @@ internal PreparedStatement? PreparedStatement
         get => _preparedStatement is { State: PreparedState.Unprepared }
             ? _preparedStatement = null
             : _preparedStatement;
-        set => _preparedStatement = value;
+        private set => _preparedStatement = value;
     }
 
     PreparedStatement? _preparedStatement;
@@ -274,7 +274,11 @@ internal void ApplyCommandComplete(CommandCompleteMessage msg)
         OID = msg.OID;
     }
 
-    internal void ResetPreparation() => ConnectorPreparedOn = null;
+    internal void ResetPreparation()
+    {
+        ConnectorPreparedOn = null;
+        PreparedStatement = null;
+    }
 
     internal void PopulateOutputParameters(NpgsqlDataReader reader, ILogger logger)
     {
diff --git a/src/Npgsql/NpgsqlCommand.cs b/src/Npgsql/NpgsqlCommand.cs
index ffbf86029f..8ddbb2e5fb 100644
--- a/src/Npgsql/NpgsqlCommand.cs
+++ b/src/Npgsql/NpgsqlCommand.cs
@@ -406,7 +406,12 @@ internal CommandState State
         }
     }
 
-    internal void ResetPreparation() => _connectorPreparedOn = null;
+    internal void ResetPreparation()
+    {
+        _connectorPreparedOn = null;
+        foreach (var s in InternalBatchCommands)
+            s.ResetPreparation();
+    }
 
     #endregion State management
 
@@ -873,7 +878,7 @@ async Task Unprepare(bool async, CancellationToken cancellationToken = default)
                     if (!pStatement.IsExplicit)
                         connector.PreparedStatementManager.AutoPrepared[pStatement.AutoPreparedSlotIndex] = null;
 
-                    batchCommand.PreparedStatement = null;
+                    batchCommand.ResetPreparation();
                 }
             }
 
@@ -1441,8 +1446,6 @@ internal virtual async ValueTask<NpgsqlDataReader> ExecuteReader(bool async, Com
                             {
                                 if (batchCommand.ConnectorPreparedOn != connector)
                                 {
-                                    foreach (var s in InternalBatchCommands)
-                                        s.ResetPreparation();
                                     ResetPreparation();
                                     goto case false;
                                 }
@@ -1455,8 +1458,6 @@ internal virtual async ValueTask<NpgsqlDataReader> ExecuteReader(bool async, Com
                             if (_connectorPreparedOn != connector)
                             {
                                 // The command was prepared, but since then the connector has changed. Detach all prepared statements.
-                                foreach (var s in InternalBatchCommands)
-                                    s.PreparedStatement = null;
                                 ResetPreparation();
                                 goto case false;
                             }
diff --git a/src/Npgsql/NpgsqlDataReader.cs b/src/Npgsql/NpgsqlDataReader.cs
index 94499c14ae..55753dc7f6 100644
--- a/src/Npgsql/NpgsqlDataReader.cs
+++ b/src/Npgsql/NpgsqlDataReader.cs
@@ -559,8 +559,6 @@ async Task<bool> NextResult(bool async, bool isConsuming = false, CancellationTo
                 {
                     preparedStatement.State = PreparedState.Invalidated;
                     Command.ResetPreparation();
-                    foreach (var s in Command.InternalBatchCommands)
-                        s.ResetPreparation();
                 }
             }
 
diff --git a/test/Npgsql.Tests/AutoPrepareTests.cs b/test/Npgsql.Tests/AutoPrepareTests.cs
index b35fe7c5d3..97a46ad277 100644
--- a/test/Npgsql.Tests/AutoPrepareTests.cs
+++ b/test/Npgsql.Tests/AutoPrepareTests.cs
@@ -620,6 +620,33 @@ public async Task Auto_prepared_statement_invalidation()
         Assert.DoesNotThrowAsync(() => command.ExecuteNonQueryAsync());
     }
 
+    [Test, IssueLink("https://github.com/npgsql/npgsql/issues/6432")]
+    public async Task Reuse_batch_with_different_connectors()
+    {
+        await using var dataSource = CreateDataSource(csb =>
+        {
+            csb.MaxAutoPrepare = 10;
+            csb.AutoPrepareMinUsages = 2;
+        });
+        await using var batch = new NpgsqlBatch();
+        batch.BatchCommands.Add(new NpgsqlBatchCommand("SELECT 1"));
+        await using (var connection = await dataSource.OpenConnectionAsync())
+        {
+            batch.Connection = connection;
+
+            for (var i = 0; i < 2; i++)
+                await batch.ExecuteNonQueryAsync();
+        }
+
+        dataSource.Clear();
+
+        await using (var connection = await dataSource.OpenConnectionAsync())
+        {
+            batch.Connection = connection;
+            await batch.ExecuteNonQueryAsync();
+        }
+    }
+
     void DumpPreparedStatements(NpgsqlConnection conn)
     {
         using var cmd = new NpgsqlCommand("SELECT name,statement FROM pg_prepared_statements", conn);